The present invention relates to a method for controlling transceiver units of base stations in a cellular radio system comprising at least a first base station comprising a first transceiver unit to which one or more channels have been allocated for receiving and transmitting telecommunications signals via a radio path to the mobile stations located in its radio coverage area. The invention further relates to a cellular radio system comprising a mobile exchange, a first base station communicating with the mobile exchange through a data connection and comprising at least a first transceiver unit for establishing a connection via a radio path to mobile stations located in its coverage area on one or more channels allocated to the first transceiver unit for transmitting telecommunications signals between the mobile stations and the mobile exchange, and control means for controlling the first transceiver unit.
The present invention relates to the dimensioning and management of traffic capacity in a cellular radio system, and particularly to the variations in the capacity need of the different parts in the geographical area covered by the system. In business centres, for example, the traffic capacity need is considerably greater in the daytime than in the evenings. Similarly, in suburban areas, for example, not much capacity is needed in the daytime, but in the evenings the capacity need grows as people return home from work. If, under these circumstances, the cellular radio capacity is dimensioned in accordance with the maximum capacity need, a considerable part of the system capacity will be unused for the most part of the day. Among other things, this means waste of energy since most of the system transceivers use energy continuously, even though no calls are transmitted through them. Furthermore, a data channel to the mobile exchange of the system must usually be continuously allocated to the transceivers which are not used, independently of whether telecommunications signals are being transmitted on the channel at a particular time or not. A considerable part of the existing data transmission capacity is thus unused for the most part of the day.
In prior art solutions, attempts have been made to transmit calls of an adjacent (congested) radio cell via-an antenna directed thereto from the neighbouring cell at peak times. An increase in the capacity of the congested cell to manage momentary load peaks can thus be avoided. The disadvantage of this prior art solution is, however, that the antenna which can be directed often fails to give as extensive a coverage area as the base station antenna of the cell.
There are also sectored prior art base stations where a separate additional channel unit is employed by means of relay-type connections, in other words the capacity of the additional channel unit is transferred from one sector to another in such a manner that its antenna output junction is changed by means of the relay connections. However, the geographical area where capacity variations can be implemented is extremely small, since the RF signal obtained from the antenna output of the additional channel unit can only be transmitted rather a short distance in a cable, for example, without a considerable attenuation of the signal in the cable. In practice, the alternative transmission antennas to which the additional channel unit can be connected thus have to be located extremely near each other.
An object of the present invention is to solve the above problems and provide a solution which saves resources and by means of which the transceiver units in a cellular radio system can be controlled in such a manner that the system can manage the load peaks as advantageously as possible. This object is achieved with the method of the invention, which is characterized in that said first transceiver unit is controlled on the basis of the traffic capacity need of the base station in such a manner that the first transceiver unit is deactivated when the traffic capacity need is small in the coverage area of the first base station.
The invention further relates to a cellular radio system to which the method of the invention can be applied. The cellular radio system of the invention is characterized in that the control means comprise means for deactivating the first transceiver unit when the traffic capacity need is small in the coverage area of the first base station.
The invention is based on the idea that by deactivating the excess transceiver units of a particular base station when the traffic capacity need has been reduced in the radio coverage area of the above base station, unnecessary waste of energy and resources can be avoided. The most essential advantages of the invention are thus reductions in energy waste, more economical use of transceiver units and the possibility to utilize available resources, such as data transmission connections between the base station and the other parts of the network, as efficiently as possible.
In a preferred embodiment of the cellular radio system of the invention, transceiver units are controlled in accordance with timing means. In other words, an operator can program the timing means in advance, on the basis of statistics about a particular radio cell (showing the traffic capacity used at different times of the day), for instance, in such a manner that excess transceiver units are deactivated, i.e. switched off, from a base station when the capacity need of the cell is small according to the statistics (at night or at weekends).
In another preferred embodiment of the cellular radio system of the invention, the control means control the amount of the traffic capacity of a base station in traffic use to its total capacity available. This can be performed in such a manner that, for example, a base station controller computes the ratio of the number of the traffic connections in use and available traffic channels and compares the ratio with the reference value that has been predefined by the operator. if the base station controller detects that the reference value is not exceeded, in other words most of the traffic capacity of the base station is unused, it deactivates one or more transceiver units from the base station. The present embodiment of the invention enables the activation/deactivation of the transceiver units to be based on a real traffic situation and not only on a traffic situation based on statistics.
In a third preferred embodiment of the cellular radio system of the invention the system comprises a second base station comprising a spare transceiver unit. The control means can thus activate the spare unit in the above second base station to use the channel(s) of the transceiver unit deactivated from the first base station when the transceiver unit in the first base station has been deactivated. The present embodiment of the invention enables available channels, in other words primarily frequency channels, to be used as efficiently as possible, since a released frequency channel can be re-allocated to the second base station. Traffic capacity can thus also be transferred from the first base station to the second base station when it is needed therein, without it being restricted by the number of available channels in the system, for example. Furthermore, the spare unit in the second base station can operate as a spare unit which is activated in the case of malfunction in a regular transceiver unit of the second base station. Instead of re-allocating an entire frequency channel, it is possible to allocate to the second base station only some of the time slots of a particular frequency channel, whereby the first and the second transceiver units can use different time slots of the same frequency channel.
In a fourth preferred embodiment of the cellular radio system of the invention the data channel (a PCM time slot, for example) that has been used by the deactivated transceiver unit of the first base station is re-allocated to the transceiver unit activated in the second base station. The existing data transmission capacity can thus be utilized as efficiently as possible.
The preferred embodiments of the method and cellular radio system of the invention are disclosed in the attached dependent claims 2 to 5 and 7 to 11.